Sulforaphane alleviates psoriasis by enhancing antioxidant defense through KEAP1-NRF2 Pathway activation and attenuating inflammatory signaling

Psoriasis is a chronic, relapsing inflammatory skin disease affecting 3–4% of the population, characterized by erythematous plaques with scaling. Multiple genetic and environmental factors contribute, but etiology remains complex. Oxidative stress—elevated ROS/RNS with diminished antioxidant defenses—damages macromolecules and activates inflammatory pathways, correlating with disease severity and promoting keratinocyte hyperproliferation. Sulforaphane (SFN), a dietary isothiocyanate from cruciferous vegetables, has potent antioxidant and anti-inflammatory activities and modulates pathways including NF-κB, HDAC, DNMT, and NRF2. The study aimed to determine whether SFN ameliorates psoriasis and to elucidate mechanisms, with a focus on the KEAP1-NRF2 antioxidant pathway and inflammatory signaling (STAT3 and NF-κB).

Prior studies implicate oxidative stress in psoriasis pathogenesis, with increased ROS and reduced antioxidant capacity in patients. ROS enhances inflammation and keratinocyte hyperplasia and is produced by activated keratinocytes, neutrophils, and lymphocytes in lesions. Exogenous antioxidants may aid management. SFN has demonstrated anticancer and anti-inflammatory effects, regulating tumor suppressor and inflammatory genes via HDAC, DNMT, and NF-κB, and activating NRF2 as well as certain microRNAs. NRF2 is crucial for oxidative stress responses, epidermal barrier formation, and keratinocyte differentiation; pharmacologic NRF2 activation (e.g., dimethyl fumarate) has clinical utility in psoriasis. However, excessive NRF2 activation may be detrimental, and SFN’s role in psoriasis had not been defined before this work.

Human samples: Skin biopsies from five psoriasis patients and five healthy donors (cosmetic procedures). Diagnosis by clinical and histological evaluation; no systemic/topical treatment for ≥2 weeks prior. Ethical approvals obtained; informed consent provided. Animal model: Female BALB/c or C57BL/6 mice and NRF2 knockout mice (Nrf2−/−) housed under SPF conditions. IMQ-induced psoriasis model: 62.5 mg of 5% imiquimod cream applied daily to shaved backs for 7 days; controls received petrolatum. SFN administered intraperitoneally at 5 mg/kg once daily for 7 days; control mice received saline. Disease severity scored 24 h after final dose using PASI (erythema, scaling, infiltration); spleen index calculated as spleen weight/body weight. n=5 per group unless stated. Histology and IHC/IF: Skin fixed in 10% formalin, paraffin-embedded, sectioned (3 μm), H&E staining. Immunohistochemistry for K16, K17, Ki67, NQO1. Immunofluorescence for NRF2 and phospho-NRF2. Protein analyses: Western blot of tissue/cell lysates (10% SDS-PAGE, PVDF transfer). Primary antibodies included K16, K17, NRF2, p-NRF2, IL-1β, NQO1, p-STAT3 (Tyr705), STAT3, p-NF-κB p65, NF-κB p65, p-IκBα, IκBα, GAPDH; HRP secondaries; ECL detection; densitometry via ImageJ. Gene expression: qRT-PCR using TRIzol-extracted RNA, cDNA synthesis, SYBR-based quantification on QuantStudio 5. Normalization to Actb or GAPDH. Primers provided for Il6, Il1b, Ccl2, Il17a, Il23a, NFE2L2, and controls. Relative quantification by 2^-ΔΔCt. Cell culture: HaCaT human keratinocytes cultured in high-glucose DMEM with 10% FBS and 1% penicillin/streptomycin at 37°C, 5% CO2. Psoriasis-like stimulation with IL-22 (25 ng/ml; 30 min or 24 h) or TNF-α (25 ng/ml; 30 min or 24 h) with or without SFN pretreatment. NRF2 knockdown: Lentiviral shRNA transduction targeting human NRF2 (two sequences, sh-NRF2-a/b) and scramble control (sh-C); selection with puromycin (2 μg/ml). Knockdown validated by qRT-PCR; sh-NRF2-b used for functional assays. ROS measurement: DHE staining (2 μM, 30 min, 37°C, dark) followed by confocal microscopy to assess superoxide in HaCaT cells after IL-22 ± SFN. Network pharmacology: Predicted SFN targets using SuperPred and OMIM; intersected with psoriasis-related genes from GeneCards and OMIM; constructed PPI network (STRING); Reactome pathway enrichment via ClueGO; assessed NRF2/NFE2L2 expression in skin using Human Protein Atlas and GEO (GSE119087). Statistics: GraphPad Prism 9.0. Unpaired two-tailed Student’s t-test for two-group comparisons; one-way ANOVA for multiple groups. Data from ≥3 independent experiments expressed as mean ± SD; significance at p<0.05.

- SFN significantly improved IMQ-induced psoriatic skin phenotypes in mice: reduced erythema, scaling, epidermal thickness, and cumulative PASI score (n=5; p<0.05 to p<0.001). Histology showed decreased epidermal hyperplasia and inflammatory infiltrates; spleen index unchanged. - SFN decreased keratinocyte hyperproliferation markers: reduced K16, K17, and Ki67 by IHC; reduced K16 and K17 protein by Western blot (p<0.05 to p<0.001). - SFN attenuated inflammatory signaling in vivo: reduced p-STAT3 and p-IκBα levels in IMQ-treated skin (Western blot; p<0.05 to p<0.001). - SFN downregulated proinflammatory mediators in skin: decreased Il1b, Il6, and Ccl2 mRNA by qRT-PCR (n=3; p<0.05 to p<0.001). - In HaCaT keratinocytes, SFN suppressed IL-22-induced STAT3 phosphorylation and reduced K16/K17 expression; SFN inhibited TNF-α-induced IκBα phosphorylation, reduced IL-1β, and decreased K16/K17 (p<0.05 to p<0.001). - Network pharmacology identified KEAP1-NFE2L2 (NRF2) as a top enriched pathway among SFN targets intersecting psoriasis genes. - NRF2 expression was decreased in human psoriatic lesions (HPA, GEO GSE119087); patient biopsies confirmed reduced NFE2L2 mRNA and decreased NRF2/p-NRF2 protein. - SFN increased NRF2 and p-NRF2 expression in IMQ mouse skin (Western blot, IF; p<0.001) and restored NRF2/p-NRF2 in IL-22- and TNF-α-treated HaCaT cells; SFN reduced IL-22-induced superoxide production. - NRF2 knockdown in HaCaT cells did not activate pathways basally but enhanced IL-22- or TNF-α-induced STAT3/NF-κB activation and K16/K17 expression; SFN failed to reverse these effects when NRF2 was silenced. - NRF2-deficient mice developed more severe IMQ-induced psoriasis-like lesions than wild-type and did not improve with SFN; showed elevated p-STAT3, p-p65, p-IκBα, increased K16, and minimal NQO1 induction. In wild-type mice, SFN increased NQO1 and reduced Il17a and Il23a expression; these effects were absent in NRF2-deficient mice.

The study demonstrates that oxidative stress and reduced NRF2 activity contribute to psoriasis pathogenesis. SFN ameliorated IMQ-induced psoriasis-like inflammation and keratinocyte hyperproliferation, acting through activation of the KEAP1-NRF2 pathway to enhance antioxidant defenses and by suppressing key inflammatory pathways (STAT3 and NF-κB). Restoration of NRF2/p-NRF2 and induction of downstream targets (e.g., NQO1) correlated with reduced ROS and inflammatory mediators (IL-1β, IL-6, CCL2) and normalization of keratinocyte markers (K16, K17, Ki67). Loss-of-function experiments confirmed NRF2 dependence: genetic NRF2 deletion in mice and shRNA-mediated NRF2 knockdown in keratinocytes exacerbated inflammatory signaling and negated SFN’s therapeutic effects. These findings align with clinical use of NRF2 activators (e.g., fumarates) and support NRF2 activation as a therapeutic strategy in psoriasis while highlighting concurrent inhibition of STAT3/NF-κB signaling as a mechanism of benefit.

Reduced NRF2 expression contributes to oxidative stress and inflammation in psoriasis. Sulforaphane activates the KEAP1-NRF2 pathway, reducing ROS, dampening STAT3 and NF-κB signaling, and attenuating keratinocyte hyperproliferation and inflammatory cytokines, thereby improving psoriatic phenotypes in vivo and in vitro. SFN’s efficacy is largely NRF2-dependent. These results support SFN and NRF2 pathway activation as potential therapeutic approaches for psoriasis, warranting further preclinical and clinical investigation, including chronic models and patient studies.

The models primarily reflect acute psoriatic inflammation (IMQ-induced mice and cytokine-stimulated keratinocytes), which may not capture chronic disease dynamics. Sample sizes were modest. Human validation was limited to small biopsy cohorts without intervention. Excessive NRF2 activation could have adverse effects, necessitating careful dosing and safety evaluation. Additional work is needed in chronic psoriasis models and clinical trials to determine efficacy, safety, and optimal delivery of SFN.